peripheral nerve sheath tumours, smooth muscle tumours, spindle cell lipoma, haemangiopericytoma and solitary cutaneous adult myofibroma.At present, the use of immunohistochemical markers is critical for the accurate classification of these tumours. SFTs are typically non-immunoreactive for S-100, keratin, actin, desmin, factor VIII related antigen, CD68, type IV collagen and epithelial membrane antigen. 2 Recent immunohistochemical and ultrastructural studies have shown that such tumours display the features of relative undifferentiated, mesenchymal cells with no evidence of mesothelial diferentiation. 3 These cells, known as dendritic interstitial cells, are characterized for their fibroblast-like features and CD34 positivity, and have been thought to represent fibroblastic precursors elements involved in antigen presentation within connective tissue. 3 Unfortunately, the CD34 positivity is not entirely specific for this entity as a number of other superficial soft tissue lesions, such as dermatofibrosarcoma protuberans, neurofibroma, schwannoma and spindle cell lipoma may also show immunoreactivity with this marker. 3 Therefore, CD34 is a highly sensitive, but non-specific marker for SFT. Recent investigations have shown that expression of the oncoprotein bcl-2, one of the many molecules that regulate apoptosis, is strongly expressed in SFT, whereas dermatofibroma and smooth muscle tumours are negative for this oncoprotein. In dermatofibroma protuberans and neurofibroma, the expression of bcl-2 is variable. Thus, bcl-2 protein expression can be used to fortalice, together with CD34 positivity, the diagnosis of SFT. 3 The cells of SFT also immunostain for CD99. 4 The clinical behaviour of SFT is unpredictable; therefore, complete excision and long-term follow-up should be always performed. 1
References1 Chang SE, Bae GY, Choi JH et al. Cutaneous solitary fibrous tumour with myxoid stroma. Br J Dermatol 2002; 147: 1267-1269. 2 Cowper SE, Kilpatrick T, Proper S, Morgan MB. Solitary fibrous tumor of the skin. Am J Dermatopathol 1999; 21: 213-219. 3 Hardisson D, Cuevas-Santos J, Contreras F. Solitary fibrous tumor of the skin. J Am Acad Dermatol 2002; 46: S37-S40. 4 Mahmood MN, Salama ME, Chaffins M et al. Solitary sclerotic fibroma of skin: a possible link with pleomorphic fibroma with immunophenotipic expression for O13 (CD99) and CD34.In summary, sIL-2R could be a good marker when treating PVA with NB-UVB therapy.